Electrical & Computer Engineering, Department of


Date of this Version

Spring 5-2016


A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Electrical Engineering, Under the Supervision of Professor Natale Ianno. Lincoln, Nebraska: May, 2016

Copyright © 2016 Qinglei Ma


An excellent candidate for an earth abundant absorber material is tungsten selenide (WSe2) which can be directly grown as a p-type semiconductor with a band gap value that matches well the solar spectrum. Although several fabrication methods were reported, further improvement is highly needed to make high quality WSe2 films. In addition, the numerical modelling of WSe2 solar devices is highly desired to assess the overall utility of the material. In this work, the growth and characterization of tungsten selenide thin films are investigated, as well simulations of homo- and hetero-junction devices. In the first part, the growth and characterization of WSe2 films has been studied. By means of selenization of tungsten films in a closed tube in a single-zone furnace, highly c-axis orientated P-type WSe2 thin films with a large carrier mobility have been grown. In the second part, multiple sets of simulations of the WSe2 solar cell devices are carried out by using PC1D software. Both WSe2 homo-junction devices and hetero-junction devices with an AZO window layer present high efficiency values, over 20%, at several tens of ns carrier lifetime of the absorber layer. This is in large part due to the very high absorption coefficient of WSe2 thin films.

Adviser: Natale J. Ianno